Fastening systems are widely used in a variety of applications where closure of components is required. Certain fastening systems are refastenable in that they are capable of multiple openings and closures. Items such as diapers and containers storing foodstuff or other consumer goods are commonly equipped with a fastening system and, typically, a refastenable fastening system. Such fastening systems may include a mechanical fastening system and/or an adhesive fastening system. While mechanical and adhesive fastening systems provide certain consumer benefits, each system also has significant drawbacks.
Mechanical fastening systems capable of refastenability include hook and loop fasteners and variants such as mushroom-shaped fasteners. These types of mechanical fasteners may have a tendency to attach to undesired surfaces such as clothing, carpet, or the wearer. Furthermore, hooks are generally rigid and may be a source of irritation if used in products which are placed in close contact to a wearer's skin. Another problem often associated with mechanical type fasteners is that they may become damaged during the high-speed formation process required for commercially viable manufacture of consumer goods such as diapers. For example, hooks tend to get damaged during manufacture, and other mechanical type fasteners such as buttons, tab and slots, or the like can also become damaged, torn, or otherwise impacted by high speed handling.
Another problem associated with mechanical fasteners is that they may not exhibit the requisite integrity for use in consumer goods. For example, disposable absorbent articles such as pant-type diapers may have sides secured by a mechanical fastener such as a hook and loop fastening system. However, hook and loop fastening systems may prove inadequate for the peel force demands of a pant-type diaper. If peel forces are too low, a child may be able to remove the diaper when such removal is undesired. Another potential drawback of conventional mechanical fasteners, particularly in pant-type diapers, is that such fasteners may need to be located in an area of the diaper without stretch properties. This may create a design paradox if the mechanical fastener is to be located in an area exhibiting stretch properties such as the side panels of a pant-type diaper. The compromise made is typically to limit the size of the hook and loop fastening area which results in a lack of versatility of the product and can diminish the desired fastening strength of the side panels of the article.
Like mechanical fastening systems, adhesive fastening systems also have drawbacks. One such drawback of an adhesive fastening system includes the use of a traditional adhesive that sticks to surfaces indiscriminately. Such indiscriminate adhesive fastening systems are not ideal for use in consumer products such as diapers where adhesion of the fastener to skin, hair, or clothing is undesirable.
Another drawback of adhesive fastening systems is that the system may exhibit “lock-up” after a period of time in an engaged configuration. Lock-up is the condition where an engaged fastening system will not release without some form of catastrophic failure that prohibits refastening. For example, the fastening system may tear or the adhesive may delaminate from an underlying substrate. In many consumer goods with an adhesive fastening system, lock-up is a significant problem because the consumer good is manufactured with the fastening system already engaged (i.e., pre-engaged). For example, an absorbent article with a pre-engaged adhesive fastening system can take the form of a pants-type diaper having refastenable side seams comprising an adhesive fastening system. During the manufacture, transport, and storage of pant-type diapers, a pre-engaged adhesive may be engaged for several weeks or months and may experience elevated pressure and temperature.
Time, temperature, and pressure may all exacerbate adhesive lock-up. Generally, a pre-engaged adhesive fastening system will experience environmental factors during transport and storage that far exceed the environmental factors experienced during use of the pre-engaged adhesive fastening system. For example, during transport and storage, a pre-engaged adhesive fastening system on a pants-type diaper may experience temperatures in excess of 60° C. and pressures in excess of 0.8 N/cm2. Conversely, during wear, a pre-engaged adhesive fastening system on a pants-type diaper generally experiences temperatures of about 98° F. (about 37° C.) and de minimis pressures. As a result of the time, temperature, and pressure experienced by the pre-engaged adhesive fastening system, a consumer may receive a pants-type diaper with a locked adhesive fastener. The diaper would be considered undesirable since unfastening the pre-engaged system would prevent further refastenability of the diaper.
Even if lock-up does not occur, the pre-engaged adhesive fastening system may require separation forces that exceed a preferred range. Consumer testing has shown that fastening systems that exhibit a peel force of greater than about 12 N/inch, as measured by a T-Peel test, are viewed as being difficult to separate. Consumers tend to prefer a fastening system exhibiting a peel force of less than 10 N/inch, as measured by the T-Peel Test.
A further drawback of pre-engaged adhesive fastening systems is that, if the system does not exhibit lock-up or require an excessive separation force, the system may exhibit poor refastenability. After a pre-engaged adhesive fastening system has been opened and refastened, the system should exhibit sufficient integrity such that it may remain engaged during use. The force to disengage the pre-fastened system should be sufficient to counteract the forces normally encountered during use of the fastening system. For purposes of pants-type diapers, the refastened adhesive fastening system should have sufficient strength to counteract normal wear forces (e.g., wearer movements) while remaining sealed. Furthermore, with regard to pants-type diapers, the fastening system should be able to be refastened at least three times while maintaining sufficient strength.
While the problems associated with mechanical and adhesive fastening systems have been presented in regard to pant-type diapers, the problems are equally applicable to similar fastening systems on other consumer and commercial products. For example, the fastening system may itself be a commercial good in the form of a rollstock of pre-engaged two-component tape such as a hook-and-loop tape with a hook-bearing sheet joined to a loop-bearing sheet. The rollstock may be used by a consumer to refastenably join two surfaces together. Other consumer products having similar problems with mechanical and adhesive fastening systems include overwraps or bags where resealability is desired. For example, fastening systems are becoming increasingly common on foodstuff bags (e.g., potato chip bags and the like) and on overwraps or bags housing consumer or commercial goods (e.g., diaper overwraps, tissue overwraps, and the like).
Accordingly, it would be desirable to provide a pre-engaged fastening system that, after aging, does not exhibit lock-up and that does not require excessive force for separation. It is also desirable that the pre-engaged fastening system is non-tacky. It is also desirable that the fastening system exhibit refastenability such that the fastening system can be opened and refastened multiple times while maintaining sufficient integrity in the refastened state. Pre-engaged adhesive fastening systems are desirable because, in a pre-engaged configuration, the adhesive surface is not exposed to contamination during shipment and handling.
It is also desirable to provide consumer goods comprising a pre-engaged fastening system that does not exhibit lock-up, does not require excessive force for separation, and exhibits requisite refastenability. A pre-engaged adhesive fastening system may impart desirable characteristics to a product that incorporates such a system. With regard to absorbent articles such as pant type-diapers, by employing various types of non-tacky adhesive fastening techniques either alone or in combination with other fastening techniques, the articles described herein offer improved versatility, fit, and refastening performance over those previously known in the art. These and other advantages of the present invention will become apparent in light of the description below.